robinson



3 Sheets-Sheet 1.

(No Model.)

M. H. ROBINSON. EXPANSION GEAR FOR ENGINES. No. 521,573. Patented June19, 1894.

' (No Model.)

M. H. ROBINSON.

3 Sheets-Sheet 2.

EXPANSION GEAR FOR ENGINES.

Patented June 19, 1894.

(Nd Model.) 3' Sheets-Sheet 3.

' M. H. ROBINSON.

EXPANSION GEAR FOR ENGINES.

No. 521,573. Patented June 19; 1894.

l Jaw i my fifi 7% [7am Mn/Mmh UNITED- STATES PATENT OFFICE.

MARK HEATON ROBINSON, OF THAMES DITTON, ENGLAND, ASSIGNOR TO WILLANS &ROBINSON, LIMITED, OF SAME PLACE.

EXPANSION-GEAR FOR ENGINES.-

SPEGIFIOATION formingpart of Letters Patent No. 521,573, dated June 19,1894. Application filed March 5. 1894. smart). 502,432. (NomQdeL) .Toall whom it may concern:

Be it known that I, MARK HEATON ROBIN- SON, engineer, a subject of theQueen of Great Britain, residing at Ferry Works, Thames Ditton, in thecounty of Surrey, England, have invented certain new and usefulImprovements in Automatic Variable-Expan sion Gear for Steam and otherFluid-Pressure Engines, of which the following is a specification.

First. In automatic variable expansion gear constructed according tothis invention the governor acts by any ordinary mechanism upon athrottle valve, and thepoint of out off is varied by the change in thesteam chest pressure following upon the closing or opening of thethrottle valve. The rod which controls the out off gear is attached to apiston working in a cylinder; one end of the cylinder is open to thesteam chest, the other is normally exposed to the boiler pressure; infact the two ends of the cylinder are normally in communication with thetwo sides of the throttle valve. The efiective area of the piston isgreatest on the side next to the steam chest; the effective area of theother side being reduced by a trunk or tail rod, or equivalent device.The cut off gear is so arranged that cut off is made earlier by thepiston moving toward the steam chest: later when it moves in thecontrary direction. 7

Second. The action is as follows :Suppose the engine to be loaded tonormal full load, the passage through the throttle valve being fullyopen, and the cut 0E gear in the desired position for normal full load.On a reduction of load taking place the increase of speed and consequentopening of the governor balls, closes the throttle-valve, and therebycontrols the engine; the pressure in the steam chest falls at the sametime, and if the change is sufficiently great, the piston above referredto, being exposed to boiler pressure, upon one side and to the nowreduced steam chest pressure upon the other, moves toward the steamchest, and by suitable mechanism makes'the out off earlier; this motion,by well understood means which need not be described, may, if desired,be caused to take place slowly. As the out off becomes earlierthe speedtends to diminish, and' the governor then opens the throttle valvewider, thus increasing the steam chest pressure and again making the cutoff later, and when the' alteration in the cut 0% ceases, owing tocomparative equalization of pressure upon the two sides of the piston,the throttle valve and the governor balls, will be nearly in theiroriginal position, the only change being that the throttle valve has tobe a little more closed than before, on account of the smaller quantityof steam required by the engine per unit of time. Owing to thedifierence in the effective areas of the two sides of the piston, thelatter will not move toward the steam chest, unless there is asubstantial preponderance of pressure on the boiler side of it. The samedifference of area insures that the piston shall move away from thesteam chest though the preponderance of pressure is still on the otherside, if that preponderance is only small. There is of course adifference of pressure (extending through a range of a few pounds persquare inch) which fails to overcome the friction of the piston and outOK gear. Hence when the preponderance of the boiler pressure over thatof the steam chest exceeds a certain amount, the cut off is madeearlier; when it falls below a certain other (and lower) amount the cutoff is made later. It is obvious that the necessary tendency to moveaway from the steam chest maybe given by other means than by adifierenceof effective area between the two sides of the piston, as bythe action of a spring or weight.

Third. Suppose the engine to be running with a light load and with ofcourse, an early out off, the difference of pressure upon the two sidesof the piston being such that it moves in neither direction. increase ofload to take place; the consequent closing of the governor balls opensthe throttle valve wider and the pressure in the steam chest isincreased; as soon as it becomes nearly the same as that on the fartherside of the piston, the latter is driven away from the steam chest, andthe out off is made later. The cut off may now be too late, but this isnot a source of trouble, because the engine is controlled by throttlevalve which by reduc ing the pressure in the steam chest graduallybrings the cut off back to a point as late as is consistent with thethrottle valve returning Imagine now an to an approximately full openposition. In a single acting engine of the central valve type such as isdescribed in the specification of a prior patent, No. 339,242, issued onthe 6th of April, 1886, in which the valves work within a hollow pistonrod which itself moves up and down within a hollow sleeve in the steamchest the sleeve may be made free to rotate. If ports inclined on oneside edge be cut in the sleeve and corresponding ports in the hollowpiston rod of the engine the admission of steam from the steam chest tothe hollow piston rod can be cut off earlier or later by turning thesleeve and this turning movement may be given to the sleeve bycouplingit to the rod hereinbefore mentioned which is moved to and froby the variations of pressure in the steam chest.

The drawings annexed show the invention applied to a single actingengine of the central valve type such as is described in the abovementioned patent.

Figure 1 is a front elevation of the engine. Fig. 2 is an elevationpartly in section and on a larger scale of the steam chest and Fig. 3 isa horizontal section of the same.

A is the crank shaft of the engine.

B B are two sets of cylinders the cylinders in each set being one abovethe other.

C (see Fig. 2) is the upper end of the hollow piston rod of one setwhich as described in the above mentioned patent rises up into the steamchest D.

E is a sleeve surrounding the upper end of the piston rod, it is free toturn but not to move up or down. In it are oblique ports E'correspondiugoblique ports are also cut in the hollow piston rod.

F is a governor which may be of any ordinary construction acting on arod G which at its upper end carries the throttle valve II.

I is the steam supply pipe.

K K (see Fig. 3) are links connecting arms on the sleeves E to a cranklever-L which can be rocked on its fulcrum L.

M is a cylinder extending outward from the steam chest.

N is a piston working therein the piston rod N of this piston hasprojections standing out from it which enter radial slots in one of thearms of the lever L.

O is a valve through which steam can pass freely from the steam chest tothe inner end of the cylinder M but which stops all passage of steam inthe reverse direction.

0' is a small passage which allows steam to pass slowly from thecylinder M to the steam chest when the pressure in the steam chest islower than in the cylinder.

P is a pipe admitting steam from the steam supply pipe I to the outerend of the cylinder M.

Q is a trunk or tail rod from the piston N passing through the cylindercover.

When the oblique ports in a sleeve E and hollow piston rod 0 areopposite to one another steam is admitted to the interior of the pistonrod and thence by other ports in the rod to the cylinders B of theengine as described in the above mentioned patent but when through thedescent of the piston rod the ports in it have passed below the ports Ein the sleeve steam is cut off.

It is obvious that the point of cut off may be varied by rotating thesleeve upon its axis thus causing the ports in the hollow piston rod topass below the oblique lower edges of the ports E either earlier orlater in the stroke according as the sleeve is rotated one way or theother. When the piston N moves toward the steam chest the sleeve isthereby turned in a direction to make the out 013? become earlier and asit moves away to become later. The outward movement to make the cut-offlater can take place quickly as steam can pass quickly from the steamchest to the inner end of the cylinder M through the valve. An inwardmovement to make the cut off earlier takes place slowly as the steam inthe inner end of the cylinder M can only pass from it into the steamchest through the small passage 0'.

Any equivalent device for controlling the motion of the piston N so thatthe outward movement of the piston may be quick and the inward movementslow may be used instead of the above arrangement.

What I claim is- 1. The combination of a steam (or other fluid) enginecylinder steam chest, pipe supplying steam thereto, throttle valve andgovernor acting thereon-valve for controlling passage of steam tocylinder-cut oh? valve for controlling passage of steam to first valve-acylinder open at one end to steam chestand at the other to steam supplypipe-a piston working therein and connec tions from piston to cut olfvalve whereby an inward movement of the piston toward the steam chestshifts the cut oflf valve in a direction to make the cut off earlier andan outward movement in a direction to make it later.

2. The combination of a steam (or other fluid) engine cylinder, steamchest-pipe supplying steam thereto, throttle valve and governor actingthereon, hollow piston rod of piston working in cylinder extending intothe steam chestsleeve in steam chest surrounding the end of the hollowpiston rod-oblique ports in sleeve and in piston r0da cylinder open atone end to steam chest and at the other to steam supply pipe-a pistonworking therein and connections from the piston to the sleeve whereby aninward movement of the piston turns the sleeve in a direction to makethe cut off earlier and a movement in the opposite direction to make itlater.

3. The combination of a steam (or other fluid) engine cylinder, steamchest-pipe supplying steam thereto, throttle valve and governor actingthereon, hollow piston rod of piston working in cylinder extending intothe steam chest-sleeve in steam chest surrounding the end of the hollowpiston rod-oblique ports in sleeve and in piston rod-a cylinder open atone end to steam chest and at the other to steam supply pipe-a pistonworking therein and connections from the piston to the sleeve wherebyaninward movement of the piston turns the sleeve in a direction to makethe out 0E earlier and a movement in the opposite direction to make itlater and means for causing any inward movement to 10 take place slowlywhile the outward movement is left free totake place quickly.

MARK HEATON ROBINSON. Witnesses:

ROBERT E. RANSFORD, T. F. BARNES.

